Antistatic carpet and method of fabrication



United States Patent ABSTRACT OF THE DISQLURE An antistatic carpet fabricated from a blend of a first fiber material which is positive with respect to leather in the tribe-electric series and a second fiber material which is negative with respect to leather in tribo-electric series.

The present invention relates generally to a method for controlling the generation of tribo-electrie charges of static electricity and more particularly to a method for producing carpets having excellent antistatic characteristics.

In the past, considerable research, attention and effort have been directed by the textile industry to the problem of eliminating or reducing friction produced static electricity in carpets. Que solution that has been proposed by a number of workers in the field involves the application of a surface spray coating which sufficiently increases electrical surface conductivity of the fibres so that electric charges produced by frictional contact with leather shoe soles are quickly redistributed and dissipated. The recognized problem with such coatings is that they are removed by vacuum sweepers and normal trafiic wear and the carpets must therefore be retreated at regular intervals.

Another proposed solution is that of mixing conductive metal fibers (i.e., stainless steel, copper, etc.) in with the conventional textile fibers or filaments to increase the carpet electrical conductivity. Production of such carpets has been found to be expensive and the problem of increased wear and duiling of expensive cutting blades in the manufacture of the carpets is now believed to be a troublesome one.

It is an object of the present invention to provide a method of fabricating carpets from conventional textile materials using normal manufacturing techniques, which carpets will permanently exhibit greatly improved antistatic characteristics.

ln accordance with the present invention, a carpet having a greatly improved antistatic characteristic is provided by blending two different suitable carpet fibers together which are selected on the basis of their relative positions in the tribo-electric or electro-static series with respect to leather so that a net zero electrical charge is accumulated on leather shoe soles frictionally contacting the composite rug surface. It is generally known that when two different materials are rubbed together, one becomes positively charged and the other correspondingly negatively charged. Charts have been prepared by workers in the textile field relating various materials in a series which has become known as a tribe-electric or electro-static series. From such a series one can predict that when any two materials in the series are rubbed together, the higher one will become positively charged and the lower one will become negatively charged. Described otherwise, the higher more positive A (above) material in the series is a donor of electrons to the lower B (below) material which accepts and temporarily holds the donated electrons.

By properly blending two selected fibers, an A fiber or filament which is above leather in the electro-static series with a B fiber or filament which is below leather in the series, it is possible, in accordance with the present invention, to provide a carpet which produces a neutral or net zero transfer of electrical charge to the leather shoe soles of persons walking on the carpet. In other words,

the A material donates substantially the same number of electrons to the leather soles as are removed or accepted from the leather by the lower B material. With the desired blend of selected A and B fibers, the net transfer of electrical charge to leather shoe soles produced by frictional contact with the surfaces of the blended fibers is substantially zero and electrical shock annoyance is thereby eliminated.

Suitable A materials which are more positive than leather in the tribo-electric series include, by way of example, wool and nylon. Suitable B materials which are more negative than leather in the tribe-electric series include, by way of example, Dacron (copolyester of ethylene glycol and terephthalic acid), Orlon (vinyl polymer of acrylo-nitrile), Velon (vinyl copolymer of vinylidene chloride and vinyl chloride), Dynel (vinyl copolymer of acrylonitrile and vinyl chloride), polyvinyl-chloride, polyethylene and polypropylene.

Using a blend of nylon (A material) and Dynel (B material) with the surface areas of the A and B materials proportioned in approximately a 1:2 ratio, the frictional charge produced on shoe soles contacting the composite surface was measured as substantially zero.

Using a blend of wool and Dynel, the optimum ratio of surface areas was measured as being approximately 1:1. By altering the optimum ratio to favor the A material, the transfer of a net negative charge to shoe soles rubbed on the carpet can be readily measured with respect to ground by holding the input probe of a vacuum tube voltmeter in the wearers hand and grounding the return terimnal. in like manner, if the optimum ratio of surfaces is altered to favor the B material, the transfer of a net positive charge results and this is readily measured.

Thus, it is apparent that optimum blends of various A material and B material combinations may be readily determined by relatively simple measurements either as described above or by the use of available laboratory electrometer apparatus such as that described by S. P. Hersh and D. I. Montgomery in an article entitled Static Electrification of Filaments Experimental Techniques and Results, published in Textile Research Journal, vol. XXV, No. 4, April 1955.

In many applications, it may be preferred to combine the A and B fibers or filaments together to form a composite yarn from which the antistatic carpet may be fabricated. In other applications, it may be preferable to fabricate the antistatic carpet from separate yarns of A and B materials. In the latter case, the pattern distribution of the separate A and B materials should preferably be small relative to the average area of a shoe sole so that the predetermined desired ratio of surface areas is substantially constant and independent of position or angular orientation of contacting shoe soles.

While preferred embodiments of the present invention have been described, it will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention as defined in the claims.

What is claimed is:

l. The method of making an antistatic carpet comprising the steps of:

(a) selecting a first fiber material A which is positive with respect to leather in the tribo-electric series,

(b) selecting a second fiber material B which is nega tive with respect to leather in the tribo-electric series, and

(c) fabricating a carpet with a blend of the A and B fibers so proportioned that the respective surface areas of the A and B fibers produce a nominal zero tribo-electric charge on leather shoe soles frictionally contacting the carpet surface.

3 2. The method of making an antistatic carpet comprising the steps of:

(a) selecting a first fiber material A which is positive With respect to leather in the tribo-electric series, (b) selecting a second fiber material B which is negative with respect to leather in the tribe-electric series, and (c) fabricating a composite carpet with the A and B fibers proportionally blended so that the electron charge transferred to and from contacting leather shoe soles with respective A and B surfaces is substantially neutralized. 3. A composite yarn for use in the manufacture of antistatic carpets comprising:

(a) a blend of a first fiber material A which is positive With respect to leather in the tribO-electric series with (b) a second fiber material B which is negative with respect to leather in the tribe-electric series,

(1 (c) the blend being so proportioned that the respective surface areas of the A and B fiber materials produce a nominal zero tribo-electric charge on leather shoe soles frictionally contacting the yarn surface. 4. An antistatic carpet fabricated from a blend of a first fiber material A which is positive with respect to leather in the tribo-electric series with a second fiber material B which is negative with respect to leather in the tribe-electric series, the blend being so proportioned that the respective surface areas of the A and B fiber materials produce a nominal zero tribo-electric charge on leather shoe soles frictionally contacting the carpet surface.

No references cited.

MILTON O. HIRSHFIELD, Primary Examiner.

J. A. SILVERMAN, Assistant Examiner. 

